feat(api): add v2 send event endpoint (#4724)

## Description

adds a send event endpoint to the v2 api and cli/mcp.

mono side pr is [here](https://github.com/inngest/monorepo/pull/8185).

## Release note

Added a send event endpoint to the v2 rest api, cli and mcp. 

`POST` `/v2/events`

```
inngest api --prod send-event \
  --name "app/user.created" \
  --data '{"userId":"user_123","email":"ada@example.com"}' \
  --id "user-created-user_123"
```



## Migration note

None.

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